The use of animal models for preclinical therapeutic testing is a powerful approach, if the model(s) used are accurate mimics of the human disease in question. Many researchers have used histological assessments of tumors coming from Genetically Engineered Mice (GEM) as a means of linking specific mouse models to known human disease subtypes. We have developed a complementary approach based upon genome-wide gene expression profiling where we objectively compare the genomic profiles of mouse tumors coming from a given organ system (i.e. breast) versus human tumor profiles, and have been able identify specific GEM models which best mimic human disease subtypes. We propose to continue and extend these genomic validation studies to include additional models of breast carcinoma and to extend our studies to models of lung cancer with the goal of using the most appropriate models for pre- clinical therapeutic trials of immune checkpoint inhibitors given the tremendous clinical importance in this area. GEM models present an advantage over other pre-clinical models like PDX or human cell line models in that they are host is immunologically intact. We propose to study the immune microenvironment in these GEM models to identify mechanisms of immune evasion and predictive signatures for response to immune checkpoint inhibitors that can ultimately be applied to human clinical trials.